When a road is cut in the side of a hill or mountain, drainage ditches are usually required to carry away water flowing down the hill or mountain towards the road. Such ditches usually have a V-shaped cross-sectional configuration which tends to concentrate water into a small area of the ditch increasing the likelihood of erosion. With a view to reducing or preventing erosion, it is preferable that the bottom of drainage ditches be round so that the flow of water is spread over a greater area, without under-cutting the embankment.
Round bottom ditches have conventionally been cut using excavators, backhoes or other mechanical digging machines having extensible or articulated booms to the distal ends of which are mounted buckets of known type. The machine is parked on the shoulder of a road, the boom and bucket is extended toward the proposed ditch area, the bucket is dropped or forced downwardly into the soil and curled inwardly and the boom is simultaneously retracted. The process is repeated two or three times. During the first pass or passes, the soil is disrupted. The number of such passes required to loosen the soil is dictated by a number of factors including the nature or rockiness of the soil, its compaction, the angle of attack of the edge of the bucket engaging the soil, the available power of the machine which may be applied downwardly on the bucket, and so on. The last pass or passes serve to scoop and clear the loosened soil. Completion of the passes may be considered as a cycle. In the case of conventional square sided buckets, with each cycle a ditch segment the width of the bucket is completed. Conventional square sided buckets are approximately five feet wide, and accordingly each cycle produces approximately five feet of ditch. At the usual speeds, a round bottomed ditch can be produced at a rate of approximately 50 lineal meters (approximately 150 feet) per hour.
The conventional ditch digging method described above with respect to square sided buckets suffers from the disadvantage that the simultaneous curl and retraction of the boom and bucket must be controlled accurately which may be difficult for an inexperienced operator. If the curl and retraction are not accurately controlled, the ditch may be over-cut resulting in undermining and premature ditch erosion. Moreover, in order to cut a ditch using the conventional method, the body of the digging apparatus must be swung out into the roadway which results in a hazard to traffic passing on the roadway. Additionally, after each cycle the machine must be moved along the road so as to present the bucket parallel to the road for the next adjacent five foot segment.
It was consequently an improvement in the art of digging ditches to introduce the apparatus which formed the subject of U.S. Pat. No. 5,353,531, which issued to Doucette on Oct. 11, 1994 for an invention entitled Ditch Digging Apparatus and Method. That patent disclosed and claimed the use of a so-called “two-pass” bucket having a square lower corner at one end of the bucket and a curved lower corner at the opposite end of the bucket. When used on a Gradall™-type machine, that is a machine able to rotate the bucket one hundred eighty degrees about the longitudinal axis of its telescopic boom, the square corner was used to loosen the soil on a first pass and the round corner to scoop a round bottom ditch on the second pass. In particular that invention related to a bucket for use on a mechanical ditch digging apparatus where the bucket included top wall means; bottom wall means; rear wall means extending between the top wall means and the bottom wall means; first side wall means extending forwardly from one end of the rear wall means and interconnecting one end of the top wall means and one end of the bottom wall means; and second side wall means extending forwardly from the other end of rear wall means and interconnecting the other end of the top wall means and the other end of the bottom wall means. The top wall means, bottom wall means and side wall means were disclosed as having front edges defining an open front end for receiving earth; the first side wall means defining a square corner with the one end of the bottom wall means, whereby the bracket could be dragged through the earth with the angular corner extending downwardly to form an angular ditch; and the second side wall means defined a convex corner at the other end of the bottom wall means. Thus, when the bucket was rotated one hundred eighty degrees around a longitudinal axis generally parallel to the boom and extending between the side walls, the convex corner extended downwardly for dragging through the angular ditch to form a round bottom ditch.